The Complementarity Plot (CP) plots the surface and electrostatic complementarity of residues buried within proteins. There are actually three plots each corresponding to a given range of burial (CP1, CP2, CP3 for burial bin 1, 2, 3 see Ref). Each point in the plot stands for an amino acid residue which can be located in one of the three regions : probable, less probable, improbable. CP is a sensitive indicator of the harmony or disharmony of interior residues with regard to the short and long range forces sustaining the native fold.